The present invention relates to a granulation processing technology of powder grains, and more particularly to a technology effective in the case of granulating spherical particles of medical supplies, foodstuffs and the like by a centrifugal tumbling granulating apparatus.
Conventionally, there have been many types of power grain granulating apparatuses, and granulation processing is performed by various methods such as a tumbling granulating method, an agitating granulating method, an extruding granulating method, a disintegration granulating method, a fluidized bed method or the like by using these apparatuses. Among these methods, the most optimum method of obtaining spherical or nearly spherical grains is the tumbling granulating method that granulates the powder during tumble. A tumbling granulating apparatus for performing this is roughly classified into the following two types. That is, there are a type of rotating a container body f formed in a drum shape, an oblique shape, an oblique cone shape or the like, and a type of disposing a rotating disk on a bottom portion of a cylindrical container and of tumbling powder grains thereon, for example, similarly to an apparatus that has been disclosed in Japanese Patent Publication No. 46-10878 or Japanese Patent Publication No. 46-22544.
The apparatus that is the type of rotating the container is mainly used in granulation of ores, fertilizers or the like, and generates relatively large particles existing within a wide range of a particle size distribution. On the other hand, the apparatus that is the type of rotating the disk is also called a centrifugal tumbling granulating apparatus (hereinafter denoted briefly by a CF apparatus), and gives particles centrifugal force caused by rotation of the rotating disk and thereby performs spherical granulation. Therefore, the apparatus of this type can obtain small granulated substances existing within a narrow range of the particle size distribution, and so is generally used in fields of medical supplies, foodstuffs or the like.
In the CF apparatus combining the cylindrical container and the rotating disk with each other, a narrow annular slit is formed between an inner wall of the cylindrical container and an outer edge portion of the rotating disk. The above-mentioned slit has a narrow width in order to prevent particles in the container from falling from the rotating disk, and can supply air thereto in a down to up directions. Further, in the CF apparatus, since the rotating disk is rotated during supply of air into this slit, the particles on the rotating disk is tumbled by using the centrifugal force and thereby performs the spherical granulation.
However, in the CF apparatus like this, since the slit formed around the rotating disk has a narrow width, flow amount of air (slit air) passing through the slit is small and so hardly contributes to drying of particles generated. Accordingly, the CF apparatus itself is poor in a capacity of drying, and the generated spherical particles are transferred to another drying device and thereby are dryly processed. That is, the generated particles are taken out of the CF apparatus, and are dried in another fluidized bed device or the like, and are formed into products. Therefore, the good spherical particles have been obtained, but there arises a problem of productivity. So, improvement thereof is desired.
Thereupon, as disclosed in Japanese Patent Publication No. 61-8736, Japanese Patent Laid-Open No. 62-65729, Japanese Patent Laid-Open No. 59-49838 or the like, a tumbling granulating apparatus combining a cylindrical container and a rotating disk with each other has been developed by adding a drying function thereto, and has recently been sold at markets as a multifunction type granulating coating apparatus. For example, a Spir-A-Flow (a trade name) or the like made at Freund Industrial Co, Ltd. is an example thereof. In the apparatus of this Spir-A-Flow, a ventilation portion is provided in a rotating disk, and air is introduced from a down direction of this ventilation portion, such that granulation and drying processings can be performed inside the same apparatus. That is, such the multifunction type apparatus can supply air from the above-mentioned ventilation portion along with or after the granulation processing, and thereby make the granulated substances drying. Therefore, since it is not necessary to transfer the generated substances to another drying device and to dry the generated substances, enhancement in the productivity thereof can be achieved.
On the other hand, besides the device in which the ventilation portion like this is formed, for example, a device, as disclosed in Japanese Patent Laid-Open No. 61-242628, has also been proposed such that a slit formed between a cylindrical container and a rotating disk has a wide width to increase flow amount of slit air. In this device, since powders are easy to fall from the slit in accordance with enlargement of the slit width, a slit portion is further provided with a powder fall prevention mechanism. In this apparatus, while the powders are prevented from falling from the slit portion by this mechanism, enhancement of the drying capacity is achieved by the slit air amount increased. Some of the multifunction type apparatuses described above are designed to improve the drying capacity by the slit air amount increased, too.
In these apparatuses, a fluidized layer can also be formed in the container by the increased amount of air or slit air supplied from the ventilation portion, so that it is possible to granulate particles of various shapes from heavy spherical particles to light amorphous particles. Moreover, the above-mentioned apparatuses can be used even in coating of particles, and so has widely used as multifunction type apparatuses capable of performing various granulating coating processings.
However, in manufacture of spherical particles which have small deviation from spherical form and exist within a narrow range of the particle size distribution, researches of inventors have discovered that properties of granulated substances obtained by these multifunction type apparatuses are inferior to properties of granulated substances obtained by the CF apparatus having no drying function. Recently, in particular, spherical particles that each have a small size and exist within a narrow range of the particle size distribution have been demanded in pharmaceutical manufacture. However, since such granulated substances can not be manufactured by the above-mentioned multifunction type apparatuses, improvement thereof has been required.
In the multifunction type apparatuses described above, since powder grains are subject to buoyancy by air passing through the ventilation portion or the like and is not affected by sufficient tumbling action and compressing action, the inventors have surmised that properties of granulated substances are not improved. To avoid this, however, if the circulating air amount is decreased, then powder grains can not be prevented from falling from the ventilation portion or the like and drying capacity thereof is degenerated. Therefore, it is necessary to secure the air circulating amount equal to or more than a certain volume, and properties of granulated substances can not avoid lowering in comparison with those manufactured by the CF apparatuses having no drying function.
Further, in the conventional CF apparatus, properties of granulated subjects obtained are good, but a drying function is provided therein, and so it takes time and labor to transfer the granulated subjects to another drying device as described above, and a problem of productivity thereof has not been solved.
In FIG. 5 disclosed in Japanese Patent Publication No. 46-10878 or FIG. 2 and FIG. 3 disclosed in Japanese Patent Publication No. 46-22544, an apparatus has been proposed in which an air suction port is provided in an upper space of a centrifugal tumbling granulating apparatus. However, even if the air suction port is provided at a position remote from the rotating disk in this apparatus, then the air suction port has hardly contributed to drying of granulated substances, and so this apparatus has not practically been utilized.
On the other hand, in the conventional centrifugal tumbling granulating apparatuses, the above-mentioned cylindrical container is usually formed of materials having no adiabatic characteristic such as stainless steel plate or the like, and therefore the centrifugal tumbling chamber formed above the rotating disk is directly cooled by the outside air. In order to perform a granulation processing, a coating processing and the like, substances to be processed in the container are sprayed with an aqueous solution. However, due to this, the inside of the above-mentioned container comes to a damp atmosphere, and there occur portions having a temperature of the dew point or less in the inner surface of the centrifugal tumbling chamber. And, moisture existing in the centrifugal tumbling chamber becomes dewing on these portions.
Once such dewing occurs, binder splash or powder adheres to the moisture and is dissolved therein. This results in a function as adhesive, and so the powder grains adhere thereto. And, since each of the powder grains acts as a kernel, other powder grains further adhere to the powder grains and spread over the entire inside surface of the fixed wall. Because of this, it takes time and labor to clean the apparatuses and further there arises a problem of giving bad influence on the product yield and operation efficiency of the apparatuses.
Moreover, in the centrifugal tumbling granulating apparatuses, if powder grains are easy to slip on the surface of the rotating disk, then this impedes tumbling motion thereof, and the powder grains are centrifugally tumbled and granulated or are powder-coated certainly, and rotation speed of the rotating disk can not be raised. As a result, there also arises a problem of efficiency in production. Further, since tight granules, small-quantity processing or the like is difficult to perform, improvement of production capacity has been desired.
Further, in the case of sending air onto the rotating disk from a vertical direction, air is sent linearly. Therefore, it is easy to send air through an upper portion of the rotating disk, and time required to pass through the rotating disk is likely to shorten. As a result, there have also arisen such problems that tumbling of the powder grains is not satisfactorily promoted and efficiency in processing thereof is not good. Further, since contact time between an air stream and the respective powder grains is apt to shorten, there have also arisen such problems that stay time staying in powder grain layers of the air stream becomes short, and the drying efficiency is difficult to enhance.
An object of the present invention is to provide a granulating apparatus capable of efficiently manufacturing spherical particles which each have a small particle size and exist within a narrow range of particle size distribution and have small deviation from spherical form, in a single apparatus.
Further, an object of the present invention is to prevent a centrifugal tumbling granulating apparatus having an air supply means above a rotating disk, from generating dewing in a centrifugal tumbling chamber. Further, another object of the present invention is to prevent powder grains on the rotating disk from slipping and to centrifugally tumble and granulate the powder grains certainly. In addition, another object of the present invention is to lengthen contact time between an air stream and respective powder grains and thereby to enhance drying efficiency thereof.
These and other objects and novel features of the present invention will be apparent from description of the present specification and the accompanying drawings.
A centrifugal tumbling granulating apparatus that is the present invention is characterized by a fixed wall having a grain contact portion which is in contact with powder grains and of which a horizontal section is formed at least in a circular shape; a rotating disk provided a predetermined clearance away from an inner side of said fixed wall and rotating in a horizontal direction by a rotary driving means; and an air supply means disposed above said rotating disk and close to said rotating disk, and supplying gas to an upper surface side of said rotating disk.
Due to this, the centrifugal tumbling granulating apparatus that is the present invention can, similarly to the conventional centrifugal tumbling granulating apparatus, granulate heavy spherical particles of which each particle size is small and which exist within a narrow range of particle size distribution, and further perform, in the same apparatus, granulation processing of generated substances after the granulation processing. Therefore, it is unnecessary to transfer the generated substances to other drying devices and then to perform drying processing, and so improvement of the productivity can be achieved.
In this case, said air supply means may supply gas to said rotating disk from above the central part of said rotating disk. And, said air supply means may have a cylindrical straight tube portion, and an air supply port which communicates with said straight tube portion and is disposed below said straight tube portion and of which a lower end side is enlarged in a radius direction of said portion and is formed like a cone. Further, said air supply means may supply gas to said rotating disk from above a peripheral part of said rotating disk. In addition, said air supply means may be provided to be movable in an up-and-down direction between a lower position close to said rotating disk and an upper position more remote from said rotating disk than said lower position.
In addition, said air supply means may be disposed in such a state that a part thereof enters into a particle layer of said powder grains. Due to this, since gas is introduced into particle layers and the granulated substances come to a fluidized state, drying thereof is performed more efficiently.
Then, said rotating disk may have such a vertical section that a peripheral part thereof faces a center thereof and is inclined downward, and may have a projecting portion in a central part thereof. Further, gas may be supplied to said clearance formed between said fixed wall and said rotating disk, from a lower direction thereof to an upper direction. This gas may be ordinary air, but may use air properly performed by dehumidifying, heating or the like.
In addition, said fixed wall may have a dewing prevention means for preventing an inner surface of said fixed wall from being dewed. Due to this, first, similarly to the above-mentioned case, dry air can be supplied from above the rotating disk through the air supply means, and the granulated substances is dried in the same apparatus by this dry air. Therefore, it is unnecessary to transfer the granulated substances to other drying devices and then to perform drying processing, and thereby improvement of the productivity thereof can be achieved.
And, secondly, said dewing prevention means can prevent an inner surface of the rotating disk from being dewed, and adhesion of the powder grains to the inner surface of the fixed wall is suppressed, and cleaning jobs are alleviated, and at the same time the product yield and apparatus operation efficiency are improved, and so improvement of the production efficiency or the like can be achieved.
In this case, said dewing prevention means may comprise an outer wall surrounding said fixed wall, and an adiabatic space formed between said fixed wall and said outer wall. As a result, conduction of heat is cut off in the adiabatic space, and the fixed wall is not affected by the outside air temperature, and the fixed wall can prevent the inner surface thereof from being dewed even if the fixed wall is cooled by the air.
And, said dewing prevention means may further comprise a pump device for sucking air from the inside of said adiabatic space. In addition, said adiabatic space may be filled with gas having lower pressure than atmospheric pressure. At this time, it is preferable that the gas in said adiabatic space has a pressure of 1.33 Pa or less. Due to this, since the outer circumference of the fixed wall may be surrounded with an adiabatic space which is in a vacuum state, a cutoff action of heat conduction is further strengthened and improvement of the dewing prevention effect can be achieved.
In addition, the powder contact portion of said rotating disk may be formed to have a smooth surface. And, a slip prevention means for preventing the powder grains on said powder contact portion from slipping may be provided in the powder contact portion of said rotating disk. Due to this, the powder grains are prevented from slipping on the rotating disk, and at the same time centrifugal gripping force is strengthened, and tumbling of the powder grains are activated. Therefore, the powder grains can be centrifugally tumbled and granulated certainly, and high speed rotation of the rotating disk, tight granules, improvement of processing capacity of small quantity, and the like may be achieved.
The rotating disk that should provide a slip prevention means of the present invention may be a flat plate or a inclined plate as shown in FIG. 21.
And, in this case, said slip prevention means may be a strip-like groove radially formed in the powder contact portion of said rotating disk, and said strip-like groove may be formed such that a side wall of a front side along a rotating direction of said rotating disk is smoother than that of a rear side along said rotating direction.
In addition, said air supply means may be provided with a swirl flow generating means for supplying swirl wind onto said rotating disk. Due to this, since a swirl movement can be given to the powder grains located on the rotating disk, the powder grains are wound up in a spiral rotation shape so as to twist a rope. Therefore, tumbling of the powder grains can be promoted, and improvement of processing efficiency can be achieved. Further, the air stream is prevented from blowing through straightly, and contact time between the air stream and the respective powder grains can be lengthened, and so stay time of the air stream staying in powder grain layer is lengthened, and drying efficiency can be enhanced.
And, said swirl flow generating means may be a wind introducing plate arranged in said air supply means. In addition, said air supply means may be disposed in such a state as to incline toward a rotating direction of said rotating disk from above said rotating disk, and supplies a swirl air stream onto said rotating disk. As a result, similarly to the above-mentioned case, the swirl air stream promotes the stumbling of powder grains, and can lengthen the contact time between the air stream and the respective powder grains.
On the other hand, a powder grain processing method that is the present invention and that uses a centrifugal tumbling and granulating apparatus described above is characterized by the steps of: charging the powder grains into said centrifugal tumbling and granulating apparatus; rotating said rotating disk while gas is supplied to an upper direction of said. clearance from a lower direction thereof; and supplying at least one of solvent, solution, dispersion solution, and. dissolved solution, and then performing one of granulation and coating of said powder grains.
In this case, gas may be supplied from said air supply means to dry granulated substances of said powder grains, and a swirl air stream may be supplied from said air supply means. Moreover, powders may be further supplied into said centrifugal tumbling and granulating apparatus.
In addition, said air supply means may be movably disposed between a lower position close to said rotating disk and an upper position remoter than said lower position from said rotating disk, and a drying step is performed, with said air supply means being disposed at said lower position.
Further, the granulating step or the coating step may be performed, with said air supply means being disposed at said upper position, and the granulating step or the coating step may be performed, with said air supply means being disposed at said lower position close to said rotating disk.
In the above-mentioned granulating step or coating step, granulation processing or the coating processing may be performed while gas is supplied from said air supply means, or these processing may be performed after gas stops to be supplied. The gas to be supplied may have a normal temperature or be heated.
In said drying step, it is preferred to perform drying processing while gas is supplied from said air supply means, and it is further desired that gas is heated. However, in the case of supplying dissolved substances and performing the granulation processing and the coating processing and the like, there is also the case of not heating supplied gas.